1. Field of the Invention
The present invention relates to a turntable and a disk driving device which are used to load and rotate a disk or the like, which serves as a recording and reproducing medium of a signal.
2. Description of the Related Art
In general, a compact disk player (CD player) carries out an a operation in which a CD is loaded on a turntable which is anchored to a rotational shaft of a spindle motor, in which the spindle motor is driven, and in which a signal which was recorded by an optical pickup is reproduced while the CD is rotated together with the turntable.
In order that the turntable used in this way can reliably transmit rotational torque from the rotational shaft of the spindle motor to the CD, extracting force of the rotational shaft after the rotational shaft was pressed into and mounted to an insertion hole of the turntable is strictly set to a value within a predetermined range.
Further, in order that a recording surface of the CD which is loaded and rotated on the turntable does not vibrate, a CD loading surface of the turntable is strictly set so as to be perpendicular to the rotational shaft of the spindle motor (preventing a so-called surface vibration).
Conventionally, as illustrated in FIGS. 14 through 16, a turntable 10 formed from a polycarbonate resin is used as the turntable to meet the above-described requirements.
The illustrated turn table 10 is structured by taking advantage of small shrinkage of the polycarbonate resin at the time of molding, and thereby, a good mold transferring ability thereof.
Namely, in the turntable 10, a shaft head portion 20, which fits into an unillustrated circular opening of a CD, is formed at a top portion of a boss portion 16 provided with an insertion hole 12, and a discoid table portion 18, which is provided with a loading portion 14, is provided integrally at the periphery of the shaft head portion 20.
The boss portion 16 is formed in the shape of a thick cylinder. The shaft head portion 20 of the boss portion 16 is formed thick and a cross-sectional configuration thereof is inverted V-shaped. A conical surface portion of the upper side of the shaft head portion 20 is formed as a guide portion 22 for guiding the circular opening of the CD to the shaft head portion 20. A plurality of auxiliary ribs 24 are provided at a portion of the lower side of the boss portion 16 and at an inner portion of a groove of the shaft head portion 20 whose cross-sectional configuration is inverted V-shaped.
An unillustrated iron pan, which is used to suck and hold the CD by magnetic force, is provided on the upper surface of the table portion 18 at the periphery of the shaft head portion 20. The ring-shaped loading portion 14, which stands upright by one step at the upper side of the table portion 18, is formed at the periphery thereof.
Further, gates 26 for injecting the polycarbonate resin, which has been melted within a mold for the turntable 10, are provided at portions of the table portion 18 which are hidden by the unillustrated iron plate.
When the turntable 10 of this configuration is molded and manufactured from the polycarbonate resin, since coefficient of friction of the polycarbonate resin to a metal is large, the coefficient of friction changes by a large amount in accordance with a state of surface roughness or a size of press-contacting force of the polycarbonate resin which presses and contacts the metal. Also, due to large modulus of elasticity, an error in the surface configuration of the polycarbonate resin which presses and contacts the metal cannot be absorbed. In consideration of the above-described facts, it is necessary to manufacture the turntable 10 so that extracting force of a rotational shaft when the turntable 10 is mounted to the rotational shaft of a spindle motor falls within a predetermined range. Moreover, as a material of the turntable 10, a polycarbonate resin containing glass fibers may be also used. In this case, mold shrinkage is even smaller and modulus of elasticity is even larger.
As a result, the turntable 30 is molded at high precision so that, at the time of injection molding, the surface roughness of the inner circumferential surface of the insertion hole 12, through which the rotational shaft of the spindle motor is inserted, is constant, that the inner diameter of the entire insertion hole 12 is constant, that roundness of the entire insertion hole 12 is constant, and that sink at the time of injection molding is not generated at the inner circumferential portion of the insertion hole 12.
Further, when the turntable 10 is mounted to the rotational shaft of the spindle motor, in order that the CD loading portion 14 of the turntable 10 is perpendicular to the rotational shaft of the spindle motor and surface vibrations do not occur, the turntable 10 is molded at high precision so that deformation such as warpage or the like does not occur to the CD loading portion 14 of the turntable 10 and is molded at high precision so as to maintain high perpendicularity of the insertion hole 12 to the loading portion 14.
Regarding the above-described turntable 10 formed from polycarbonate resin which is an expensive material, extremely high injection molding technique and mold management are required when the turntable 10 is manufactured. Thus, the price of the product increases.
Therefore, it is desired that the resin which is a material of the turntable 10 is a polyacetal resin or the like which is comparatively inexpensive and is widely used in general as an engineering plastic.
However, when the polyacetal resin is used as a material and the turntable 10 having the configuration shown in FIGS. 14 through 16 is subjected to injection molding, the following drawbacks may arise. First, due to the characteristic in which mold shrinkage of the polyacetal resin is large, sink at the time of injection molding is generated at the inner circumferential portion of the insertion hole 12, such that extracting force of the rotational shaft when the turntable 10 is mounted to the rotational shaft of the spindle motor may be smaller than a predetermined necessary value. Second, manufacturing error in the rotational shaft of the spindle motor is added to the generation of sink at the inner circumferential portion of the insertion hole 12 at the time of injection molding, such that the extracting force of the rotational shaft when the turntable 10 is mounted to the rotational shaft may be smaller than the predetermined necessary value.
Moreover, since the CD loading portion 14 of the turntable 10 is thick, sink becomes larger and deformation such as warpage or the like occurs easily. Further, because the boss portion 16 which is provided with the insertion hole 12 is thick, deformation due to the sink occurs and a large error is made to positional precision between the boss portion 16 and the loading portion 14. Thus, when the turntable 10 is mounted to the rotational shaft of the spindle motor, the CD loading portion 14 of the turntable 10 is not perpendicular to the rotational shaft of the spindle motor, and surface vibrations may take place.
With the aforementioned in view, an object of the present invention is to newly provide a turntable and a disk driving device using the same, wherein the turntable can be formed from a comparatively inexpensive material and is also structured so that the predetermined quality of a product can be manufactured easily and inexpensively in accordance with ordinary injection molding technique and ordinary mold management.
A first aspect of the present invention is a turntable on which a disk is loaded, the turntable comprising: a fixing portion into which a rotational shaft which rotates the turntable is pressed, the fixing portion being elastically deformable in a radial direction of the fixing portion; and a reinforcer which is provided at an outer circumference of the fixing portion, the reinforcer generating reaction force against elastic deformation of the fixing portion in the radial direction.
Due to the above-described structure, the radial direction reaction force by the reinforcer for the fixing portion and radial direction reaction force when the fixing portion is elastically deformed are applied to the rotational shaft which was pressed into the fixing portion. Accordingly, the fixing portion presses and contacts the rotational shaft strongly in the radial direction, the fixing portion sufficiently supports the rotational shaft, and extracting force of the rotational shaft which was pressed into the fixing portion can improve.
A second aspect of the present invention is a turntable, comprising: a table portion on which a disk is loaded; and a shaft supporting structural portion which is provided substantially perpendicularly to the table portion at a central portion of the table portion in order to support a rotational shaft which rotates the turntable, wherein the turntable is formed by injection molding and, when the turntable is injection molded, a gate for an injection mold is disposed in a vicinity of the shaft supporting structural portion at the central portion of the table portion.
Due to the above-described structure, the gates are provided in the vicinity of a portion at which the table and the shaft supporting structural portion intersect, and a melted resin which has been injected from the gates enters the mold linearly and reaches every corner of the mold rapidly and uniformly. The entire resin thereby solidifies uniformly. Consequently, at the time of injection molding, deformation due to sink or the like cannot occur to the inner circumferential portion of an insertion hole which is formed at a fixing portion. Therefore, extracting force of the rotational shaft which was pressed into the insertion hole of the fixing portion can improve.
A third aspect of the present invention is a turntable, comprising: a table portion on which a disk is loaded; a thin-walled cylindrical-shaped outer cylindrical portion which is provided at a central portion of the table portion and which fits into an opening of the disk; a thin-walled cylindrical-shaped inner cylindrical portion provided at an inner circumference side of the outer cylindrical portion, the inner cylindrical portion being concentric with the outer cylindrical portion and having a smaller diameter than the outer cylindrical portion; and a rib portion provided from the outer cylindrical portion to the inner cylindrical portion in a radial direction of the inner cylindrical portion.
Due to the above-described structure, the outer cylindrical portion and the inner cylindrical portion are formed thin. Therefore, when the entire table is subjected to injection molding, deformation due to warpage, sink, or the like does not occur to the outer cylindrical portion and the inner cylindrical portion. The turntable can be molded into a predetermined configuration satisfactorily and at high precision.
A fourth aspect of the present invention is a disk driving device, comprising: a rotational shaft which is connected to a spindle motor for driving to rotate a disk and which is driven to rotate by the spindle motor; and a turntable connected to the rotational shaft, on which turntable the disk is loaded, and which turntable rotates the disk, wherein the turntable includes: a fixing portion for the rotational shaft, into which fixing portion the rotational shaft is pressed, the fixing portion being elastically deformable in a radial direction of the fixing portion; and a renforcer for the fixing portion provided at an outer circumference of the fixing portion, the reinforcer generating reaction force against elastic deformation in the radial direction of the fixing portion.